1. Field of the Invention
The present invention relates to a developing solution for photolithography, a method for forming a resist pattern, and a method and an apparatus for producing a developing solution for photolithography.
2. Related Art
Recently, patterns are rapidly becoming finer due to advancement in photolithography technology to produce semiconductor elements or liquid crystal display elements. The fine patterns are achieved by miniaturizing resist patterns formed on surfaces of substrates etc. The resist patterns are prepared by forming a resist film of a resist composition containing a photosensitive compound on a surface of a substrate etc., selectively exposing the resist film with an active energy beam such as light and electron beams through a predetermined mask pattern, and performing a development processing. In this stage, a portion corresponding to a figure provided in the mask pattern becomes a resist pattern within the resist film. Then a semiconductor element is produced through a step of processing the substrate by etching using the resist pattern as a mask, for example. The resist compositions of which exposed portions become soluble in a developing solution are referred to as positive type and the resist compositions of which exposed portions become insoluble in a developing solution are referred to as negative type.
In the development processing of semiconductor element production processes, an alkaline aqueous solution of tetramethylammonium hydroxide (TMAH) is commonly used as the developing solution. TMAH is favorably used in the production of semiconductor elements since it does not contain metal ions affecting semiconductor elements. However, when integration degree of semiconductor elements is increased and the half pitch (HP) size becomes as small as 49 nm or less, a swelling phenomenon in which TMAH swells resist patterns during development is troublesome. When resist patterns are swelled by TMAH, there arises a factor to degrade reproducibility of patters so that the resist patterns degrade linearity or turn over during rinsing procedure after development.
Because of this, non-Patent Document 1 proposes to use an aqueous solution of tetrabutylammonium hydroxide (TBAH) rather than the aqueous solution of TMAH as the developing solution. The swelling phenomenon of resist patterns during development is mitigated and the reproducibility of patterns is improved by using the aqueous solution of TBAH as the developing solution.
In addition, the developing solution may be prepared in a way that the developing solution is shipped out in a concentrated condition from a manufacturer of the developing solution and the concentrated developing solution is diluted with pure water by a user to prepare the developing solution of a predetermined concentration (e.g., see Patent Document 1). The method described above is preferred from the viewpoint of reducing transportation cost of the developing solution.    Patent Document 1 Japanese Patent No. 2670211    Non-Patent Document 1 The Japan Society of Applied Physics, 70th Meeting, Extended Abstracts No. 2, p. 635, “Investigation of New Developing Solution for EUV Resist”, Semiconductor Advanced Technologies, Juliusjoseph Santillan, by Toshiro Itani